A first order sliding mode controller with appropriate parameters sliding surface (modeled in usual time domain and realized by transfer function) is considered here for LCL grid connected three phases three wires shunt active filter (SAF). If shunt active conditioners are already well known in compensation for the main types of current disturbances in the electrical power systems, it is also admitted that they generate some undesired components caused by VSI switching frequency. In order to prevent these components from spreading to the grid side, a LCL output filter is generally proposed. In this context, a VSI connected grid via a LCL filter is largely proposed for renewable energy systems, where the component to be injected into the grid is only the fundamental. Unfortunately, when the injected components include fundamental plus harmonics and for a LCL output filter associated to linear controllers, a phase shift appears, between the identified harmonics current and the injected current. This phase shift impacts negatively the current disturbances filtration and/or compensation of the SAF. Therefore, sliding mode controller with appropriate sliding surface, in both time and frequency domains, is proposed as nonlinear control method, to overcome the phase shift effects over the entire bandwidth, for the shunt active filter. Besides, a PWM-SM-Controller, with zero order hold in input of the PWM, will allow to operate in a fixed frequency, preventing a variable switching frequency effects. The rapidity, tracking and robustness of this proposed controller, within the SAF, are validated by Matlab, Simulink, Simscap-Sim_Power_System code.
The effects of measuring devices/sensors on improving the power quality (PQ) of electric networks are studied in this paper. In this context, improving the performance of an LCL-type grid connected to a three-phase three-wire shunt active filter (SAF) in the presence of voltage perturbations is studied. In order to ensure the high-quality performance of LCL-SAF in the presence of voltage perturbations, the robust continuous second-order sliding mode controller (2-SMC), including twisting and super-twisting controllers, and continuous higher-order sliding mode controller (C-HOSMC)-based approaches are employed. These controllers, whose outputs are processed by pulse-width modulation (PWM), allow minimization of the phase shift and prevent the generation of discontinuous chattering commands, which can severely damage the VSI components. Moreover, an integration of a generalized instantaneous power identification algorithm with an advanced phase locked loop (PLL) was proposed and experimentally tested to validate the effective performances of SAF under severe perturbations. Additionally, the studied approaches were tested via simulations taking into account a conventional nonlinear industrial load in a real textile factory environment, using measurements provided by power quality analyzers. Finally, the effects of the measuring devices, including the current and voltage sensors, on the accuracy and reliability of the SAF and, consequently, on the PQ of the electric power grid were studied via simulations and experimentally. The results of this study support the validity of the recently published patent.
An artificial neural network (ANN) based current controller for a high voltage direct current (HVDC) transmission link, composed of an ANN trained off-line in parallel with a robust PI controller, is described in this paper. Different ANN architectures are investigated for this ANN controller. Comparisons between the responses obtained with the PI and ANN controllers for the rectifier of a HVDC transmission system are made for various system ANN parameters (learning rate and momentum term) contingencies and it is shown that the later has many attractive features.
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